Foliar Application of Silicon Enhances Resistance Against Phytophthora infestans Through the ET/JA- and NPR1- Dependent Signaling Pathways in Potato.

Xiaojing Xue,Haifeng Liu,Zhiliang Zhang,Wei Yang,Changxiang Zhu,Zhaohui Chu,Tiantian Geng,Weiran Zhong

doi:10.3389/fpls.2021.609870

Abstract

Late blight (LB), caused by the oomycete pathogen Phytophthora infestans, is a devastating disease of potato that is necessary to control by regularly treatment with fungicides. Silicon (Si) has been used to enhance plant resistance against a broad range of bacterial and fungal pathogens; however, the enhanced LB resistance and the molecular mechanisms involving the plant hormone pathways remain unclear. In this study, Si treatment of potato plants was found to enhance LB resistance in both detached leaves and living plants accompanied by induction of reactive oxygen species (ROS) production and pathogenesis-related genes expression. Regarding the hormone pathways involved in Si-mediated LB resistance, we found a rapidly increased content of ethylene (ET) 15 min after spraying with Si. Increased jasmonic acid (JA) and JA-Ile and decreased salicylic acid (SA) were identified in plants at 1 day after spraying with Si and an additional 1 day after P. infestans EC1 infection. Furthermore, pretreatment with Me-JA enhanced resistance to EC1, while pretreatment with DIECA, an inhibitor of JA synthesis, enhanced the susceptibility and attenuated the Si-mediated resistance to LB. Consistent with these hormonal alterations, Si-mediated LB resistance was significantly attenuated in StETR1-, StEIN2-, StAOS-, StOPR3-, StNPR1-, and StHSP90-repressed plants but not in StCOI1- and StSID2-repressed plants using virus-induced gene silencing (VIGS). The Si-mediated accumulation of JA/JA-Ile was significantly attenuated in StETR1-, StEIN2-, StOPR3- and StHSP90-VIGS plants but not in StCOI1-, StSID2- and StNPR1-VIGS plants. Overall, we reveal that Si can be used as a putative alternative to fungicides to control LB, and conclude that Si-mediated LB resistance is dependent on the ET/JA-signaling pathways in a StHSP90- and StNPR1-dependent manner.

Highlights

Silicon (Si) is the second most abundant element in the earth’s crust (Brackhage et al, 2013)
By repressing the expression of ET, salicylic acid (SA), and jasmonic acid (JA) synthesis- or signal transductionrelated genes via virus-induced gene silencing (VIGS), we reveal that Si mediated resistance against P. infestans through the ET/JA- and NPR1-dependent signaling pathways in potato
It has not been reported that Si protects potato against the oomycete pathogen P. infestans, we observed that a farmer had controlled late blight on potato with the foliar spraying of fungicides containing sodium silicate (Na2SiO3)

Summary

Introduction

Silicon (Si) is the second most abundant element in the earth’s crust (Brackhage et al, 2013) It is not an essential plant nutrient; an increasing number of studies have demonstrated that it is a beneficial substance extensively used in agricultural systems to help plant adaptation to changeable environmental circumstances. The impressive beneficial effects of Si alleviate the destruction of various plant species during abiotic and biotic stresses (Li et al, 2018; Coskun et al, 2019). Si application is beneficial by enhancing plant resistance to biotic stresses. Si application has positive effects against pathogens, including viruses, bacteria, fungi and oomycetes in thirty-eight plant species (Wang et al, 2017). The preventative function of Si is overwhelmingly associated with pathogens (e.g., powdery mildews, oomycetes and rice blast fungus) that have a biotrophic phase (Kim et al, 2002; Rémus-Borel et al, 2005; Rasoolizadeh et al, 2018), while it has no effect or a negative effect on some typical necrotrophs, such as Botrytis cinerea and Sclerotinia sclerotiorum (Heine et al, 2006; Nascimento et al, 2014; Coskun et al, 2019)

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Conclusion